Iranian President-elect Hassan Rohani said that with his election his country had entered an era of cooperation and would take concrete steps to resolve its nuclear standoff with the West—promises that would require a shift by Supreme Leader Ayatollah Ali Khamenei.

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Iranian President-Elect Hassan Rohani, in white turban, prays on Sunday at the shrine of late Supreme Leader Ayatollah Ruhollah Khomeini.
European Pressphoto Agency

Mr. Rohani, in first news conference since his landslide victory in Friday's election, called for Iranian relations with the U.S., which he referred to as an "old wound," to be healed.

The U.S. and allied European and Arab governments responded cautiously to Mr. Rohani's election and statements, saying it was too early to tell whether he could chart an independent policy from the hard-line approach championed by Mr. Khamenei over the past decade.

Although Mr. Rohani isn't a radical reformer, Iranian voters saw him as a break from eight years of conservatism and defiance by President Mahmoud Ahmadinejad. Foreign policy and the economy, linked because of international sanctions over Iran's nuclear program, were top campaign issues.

President Barack Obama, after meeting with Russian President Vladimir Putin in Northern Ireland, said Monday that "we both expressed cautious optimism that with a new election there we may be able to move forward on a dialogue that allows us to resolve the problems with Iran's nuclear program."

Iran Election Watch

Learn more about the structure of the Iranian government and the candidates who ran for president.

The Islamic Republic's overarching policies on matters such as its nuclear program, relations with the U.S. and its support of Syria's regime are decided above the president's level. Mr. Khamenei and his close circle of advisers typically decide the direction of these policies, and the president executes them.

Mr. Khamenei has said over the past year that Iran would gain nothing by normalizing relations with the U.S.

Mr. Rohani, a 64-year-old cleric and lawyer, is viewed as a pragmatic and moderate politician who is trusted by Mr. Khamenei and his conservative circles as well as by Iran's reformist factions.

After serving on Mr. Khamenei's policy team for over two decades, Mr. Rohani has some influence with the supreme leader and is likely to have a freer hand than his predecessors to shape Iran's policies, many Iranian analysts said.

Conservative and hard-line factions that fought and blocked changes by President Mohamad Khatami, Iran's last reformist president, will likely be more accommodating to Mr. Rohani because of his close relationship to the supreme leader.

"Mr. Khamenei fully trusts him and once even said to him that he mentions him by name in his nightly prayers," said Seyed Hossein Mousavian, a former member of Iran's nuclear negotiating team who served as Mr. Rohani's spokesman when he served as Iran's chief nuclear negotiator in 2003-05.

But Mr. Rohani's close relationship to Mr. Khamenei could prevent him from pursuing the overhauls that Iran's opposition seeks, and make him less likely to challenge the supreme leader.

During the campaign, Mr. Rohani said the U.S. was like the world's "village elder," to whom Iran should be talking; on Monday, in the live, televised news conference, he said "Iran is not seeking to increase or expand tensions with the U.S."

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Mr. Rohani said his administration would pursue productive talks with the P5+1 group—the United Nations Security Council permanent members and Germany—and would use his experience at the negotiating table as a guideline.

Iran "will take two initiatives to remove sanctions step by step. First we will be more transparent in our nuclear program…and second we will build trust between Iran and other countries," he said. He also reiterated Iran's position that it wouldn't suspend uranium enrichment or "compromise on the rights of Iranian people."

However, he said if Iran feels as if the other side—mainly the U.S.—has "good intentions," there would be opportunity for change.

American and European officials said they were hopeful that negotiations with Tehran over its nuclear program would resume by August.

U.S. and European officials said they were looking to see who would replace the current lead negotiator, hard-liner Saeed Jalili, as an indicator of potential change.

When Mr. Rohani served as Tehran's nuclear negotiator, he oversaw a team of diplomats and technocrats who generally favored engaging the U.S. and Europe. Many of these officials were, subsequently, purged from the Iranian diplomatic corps after the election of Mr. Ahmadinejad in 2005. U.S. and European diplomats are waiting to see if some of these officials will be brought back.

U.S. and European officials said there were no plans to loosen or delay economic sanctions on Iran as a result of Mr. Rohani's election. The U.S. is set to impose new financial penalties aimed at essentially banning the use of Iran's currency, the rial, on July 1.

Still, these officials said on Monday that the countries negotiating with Iran are discussing whether to pursue a more aggressive diplomacy in the coming months.

Iran and the U.S. broke off diplomatic relations in 1979 after the takeover of the American Embassy in Tehran. The Islamic Republic has since used anti-American rhetoric as a way to show its defiance to the West and appeal to masses in the Muslim world.

Iran's core nuclear policy has centered on the Islamic Republic's insistence that it has the right to peaceful nuclear energy and enriching uranium within the framework of the Non Proliferation Treaty, to which Iran is signatory. Western countries and the International Atomic Energy Agency, the U.N. nuclear watchdog, claim that Iran's nuclear program hasn't been transparent and that Iran could eventually obtain nuclear-weapon technology.

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Mr. Rohani was vague when it came to domestic policies such as his campaign pledges to free political prisoners and open up the society, appearing cautious about upsetting the regime.

He said his administration would include technocrats from all political factions in Iran, including reformists and conservatives.

His sweeping victory over conservative rivals was largely the result of a last-minute mobilization of reformist political parties and opposition supporters.

Iran's Revolutionary Guard Corps, its volunteer million-man paramilitary unit known as Basij, and parliament have issued statements pledging their unconditional support to Mr. Rohani, suggesting conservatives are closing ranks behind him as a way to unify Iran's divided factions.

At one point during the news conference, when asked about Syria's civil war, Mr. Rohani said it was the Syrians who should choose the fate of their nation. The suggestion that citizens should determine their destiny drew applause and cheers from some members of the press corps.

When asked about political prisoners, Mr. Rohani didn't mention the names of the opposition leaders under house arrest, Mir Hossein Mousavi and Mehdi Karroubi, whose release has been the top demand of many supporters as well as reformist leaders who rallied behind him.

In a disruption that is unusual for a televised news conference in Iran, as the session came to an end, someone called out for the release of Mr. Mousavi. As an uproar erupted, the national broadcast channels airing the conference cut the sound and Mr. Rohani ended the conference and left the room.

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